A heat exchanger serves between two environments, which have a difference in temperature, to absorb heat from one side and then emit the heat to the other side. In a general air conditioning system of a vehicle including evaporator for absorbing heat from the periphery thereof, a compressor for compressing refrigerant, a condenser for emitting the heat to the periphery thereof and an expansion valve for expanding the refrigerant, the evaporator, the condenser and the like are the typical heat exchangers. In the air conditioning system, the gaseous refrigerant introduced from the evaporator to the compressor is compressed at high temperature and high pressure, and while the compressed refrigerant is liquefied by passing through the condenser, heat of liquefaction is emitted to the periphery, and the liquefied refrigerant is converted again into a low temperature and low pressure wet vapor state by passing through the expansion valve and then introduced into the evaporator so as to be vaporized. As described above, the cooling occurs substantially by the evaporator in which the liquid refrigerant is vaporized by absorbing a quantity of heat corresponding to the heat of liquefaction from the periphery, and the inside of a vehicle can be air-conditioned by air cooled around the periphery of evaporator. Further, in order to increase cooling efficiency of the air conditioning system, the condenser is generally provided at a front side of the vehicle.
In addition, the vehicle is provided with other cooling system like an oil cooler as well as the air conditioning system for cooling the inside of the vehicle. A vehicle engine or transmission is filled with oil which serves to remove friction and maintain airtight condition. If the oil is excessively heated, a viscosity of the oil is lowered, and thus it is not possible to perform its functions (i.e., removing of the friction and the maintaining of airtight condition). Particularly, since the function of removing the friction is deteriorated, it is apprehended that parts of the engine and the like may be damaged. Therefore, in order to prevent the above-mentioned phenomena, the oil cooler is used as a means for cooling the oil.
FIG. 1 is a perspective view showing an arrangement configuration of conventional oil cooler and condenser. As shown in FIG. 1A, an oil cooler 100′ is disposed at a front side of a condenser 200′ so as to partially cover a surface of the condenser 200′. A heat exchange medium (oil in case of the oil cooler and refrigerant in case of the condenser) is flowed in the oil cooler 100′ and the condenser 200′, like in a typical heat exchanger, and the heat exchange is performed among a tube, a fin and the air therearound. However, in the conventional oil cooler 100′ and condenser 200′ as shown in FIG. 1B, when the air blows to a portion where the oil cooler 100′ and the condenser 200′ are overlapped with each other, since the air should pass through the two kinds of heat exchangers, air resistance is remarkably increased and thus heat exchange performance of the condenser 200′ is considerably deteriorated. Furthermore, through a portion S of the condenser 200′, which is overlapped with the oil cooler 100′ and placed at a right rear side of the oil cooler 100′, high temperature air heated by the oil cooler 100′ passes and thus condensing efficiency of the condenser 200′ is rapidly deteriorated.
To prevent the above-mentioned problems, there has been developed a condenser which is integrally formed with an oil cooler. FIG. 2 shows the condenser integrated with the oil cooler. As shown in FIG. 2A, there are provided tubes and which are disposed in a row between a pair of tanks and which fins and are interposed therebetween, and baffles are provided in the tanks so as to divide a space for the flow of the heat exchange medium into two parts one of which is used as the oil cooler tube and the other is used as the condenser tube. That is, in the heat exchanger shown in FIG. 2, oil is flowed into the oil cooler tube forming the oil cooler 100″ and refrigerant is flowed into the condenser tube forming the condenser 200″, so that the heat exchange occurs in each of the oil cooler 100″ and the condenser 200″. The FIG. 2 shows that the oil cooler 100″ is positioned at a lower side of the condenser 200″, however, the positions thereof may be changed. However, even in case of the condenser integrated with the oil cooler, there are some problems. First, since the only way to improve the cooling performance of the oil cooler 100″ and the condenser 200″ is to change a height or a material of each tube, there is a limit to the improvement of the cooling performance.
In addition, the oil generally has a property that its viscosity is increased at a lower temperature. Therefore, in case of the cold region or the winter season that the temperature is very low, since the oil is further cooled by the oil cooler 100″ in spite that its viscosity is higher than need be at the early stage of starting, it is apprehended that parts of the engine may be damaged. This phenomenon is called “low-temperature impact”.
In the conventional condenser integrated with the oil cooler, to prevent the low-temperature impact, as shown in FIG. 2B, there is provided a bypass valve 140″. By using the bypass valve 140″, a path B through which the oil does not pass the oil cooler 100″ is selected when the viscosity is higher than a standard state, and a path A through which the oil pass the oil cooler 100″ is selected when the viscosity is in a normal state. However, when such the bypass valve 140″ is used, it further complicates control of the cooling system. Moreover, since further parts like the bypass valve 140″, which are accessorily necessary, are required, a product price is increased, and an internal space in an engine room becomes narrow.